In 4 days, Cao Bằng happened 3 strong earthquakes approximately 4 to more than 5 magnitude. The area is also believed to be the most likely place for earthquakes in Vietnam.
Around 7 am on November 28, a magnitude 4.7 earthquake occurred in Trung Khanh district, Cao Bang province with a 10 km deep epicenter. This is the third time this area has had an earthquake.
Talking to PV, Assoc.Prof. Dr. Cao Dinh Trieu, former Deputy Director of the Institute of Geophysics, said that the earthquakes that occurred continuously in this area were aftershocks of a previous large earthquake. According to his guess, it was a 5.4 magnitude earthquake on the morning of November 25.
The people of the capital constantly reflect the feeling of shaking due to the earthquakes in Cao Bang.
"After each strong earthquake, the spreading seismic waves create a lot of aftershocks. These aftershocks spread to the surrounding environment and trigger the environment, forming weaker earthquakes. The strength depends on the ability. energy accumulation and release of energy of each area, leading to smaller earthquakes after a few hours to a few days , " he said.
He emphasized that the aftershocks must be smaller than the main earthquake (aftershocks), if the latter games get smaller, people can be assured. But if among the aftershocks there is an earthquake greater than the aftershock, great care is needed.
Cao Bang area has typical energy-accumulation and tectonic characteristics, many hills and mountains are mixed with low-altitude areas, so earthquakes are easy. In addition, Cao Bang is also located on the Cao Bang - Tien Yen fault zone , running from China to Vietnam - a strong fault zone.
"This is a very wide zone, including many faults, with a complex system running from China to Vietnam. In this zone, there are 2-3 main zones and many sub-fault zones like bird's feet. often cause earthquakes, but strong battles mainly in the north, crossing the border with China, going towards Vietnam are getting smaller, "said Dr. Cao Dinh Trieu.
He added that Hanoi has almost no earthquakes due to its flat and sunken terrain, but often suffers from aftershocks causing the ground to shake due to weak ground. High-rise buildings, especially those in areas with weak soil, are easily perceived, while the surface houses are almost invisible.